Patellofemoral pain syndrome (PFP) is one of the most common causes of knee pain, affecting approximately 25% of the physically active population, with females being 2-3 times more likely to develop PFP compared to their male counterparts. The overall objective of this proposal is to determine the mechanical (structural and biomechanical) and non-mechanical (demographic and psychosocial) risk factors that are associated with PFP and identify the risk factors specific to females and males. The approach will be to use a prospective cohort design to identify risk factors that are associated with incident PFP. The central hypothesis is that individuals who develop PFP will have altered movement patterns, abnormal lower extremity anatomical alignments, decreased lower extremity strength, previous history of knee injury, previous participation in a low number of athletic activities, decreased levels of hardiness, and increased number of healthcare visits. A secondary hypothesis is that females and males will have different risk factor profiles. We will utilize baseline risk factor data that has been collected on 5690 freshman (males=3482, females= 2208) during the summers of 2005- 2008 at the following military academies: United States Naval Academy, United States Military Academy, United States Air Force Academy. Baseline risk factor data was collected through a current NIH funded project (R01-AR054061001), entitled JUMP-ACL. Each participant will contribute follow up time for incident PFP until they graduate from their respective academy. Medical record reviews will be performed to identify those participants who developed PFP during their respective follow-up time. Based on the two years for the proposed investigation, follow up time will be 4 years for all participants enrolled in the JUMP-ACL investigation from 2005-2008. Poisson regression analyses will be performed to determine the risk factors for PFP. Additionally, males and females will be analyzed separately to determine gender specific risk factor profiles. The proposed project is making an efficient use of already collected risk factor data by adding analysis of a new outcome (PFP) that would not otherwise be investigated by the JUMP-ACL project. Additionally, the proposed investigation is cost effective due to no funds being required for baseline data collection. Our rationale for the proposed investigation is that there is a crucial need for prospective studies that identify the risk factors for PFP so that more focused prevention strategies can be developed that are appropriately gender specific. PUBLIC HEALTH RELEVANCE: Patellofemoral pain syndrome (PFP) is one of the most common chronic knee conditions affecting young adults, with an increased occurrence in females. Individuals suffering from this condition may experience symptoms lasting multiple decades, limiting their participation in physical activity, and predisposing them to chronic diseases associated with inactivity such as obesity, arthritis, coronary artery disease, diabetes, and cancer. The results from this investigation may be used to identify those at greatest risk to PFP and develop appropriate prevention programs to decrease the occurrence of this condition, particularly in females.